Treatment of chips of polycarbonamide containing organic derivative of hypophosphorous acid



ceptivity of filaments made therefrom.

United States Patent TREATMENT 0F CHIPS 0F POLYCARBONAMIDE CONTAINHNGORGANIC DERIVATIVE 0F HYPO- PHOSPHURQUS ACID George H. Brinkman, Jr.,and Gerald W. Sovereign, Gulf Breeze, Fia., assignors to MonsantoCompany, a corporation of Delaware No Drawing. Filed Feb. 12, 1962, Ser.No. 172,773 7 Claims. (Cl. 260-78) The present invention relates to aprocess of treating chips of a polycarbonamide, i.e., nylon, containingan organic derivative-of hypophosphorous acid. More particularly, thepresent invention relates to a process of treating chips of a specificpolycarbonamide, namely polyhexamethylene adipamide, commonly termednylon- 66, containing a phenyl derivative of hypophosphorous acid orsalt thereof added during the polycondensation of the polymer-formingmaterial to enhance the dye receptivity of filaments made therefrom.

Manufacture of fiber-forming polyamides by polycondensation of diaminesand dibasic acids is broadly known. A commercially important polyamideof the aforesaid class is polyhexamethylene adipamide, known generallyas nylon-66. In the preparation of nylon-66, hexamethylenediammoniumadipate (the salt of hexamethylene diamine and adipic acid) isheated under suitable polycondensation conditions to produce afiber-forming polyamide having molecular weights represented byintrinsic viscosity values of about 0.3 to 1.3.

Filaments are normally made from the fiber-forming polyamides byconventional melt spinning techniques. Unfortunately, such filamentshave a limited aflinity to certain dyes. This limited afiinity of thefilaments for dyes not only restricts the depth of obtainable color, butalso greatly limits the range of dyes which can be employed.

It is known that certain additives can be incorporated in thefiber-forming polyamides to enhance the dye re- It has been suggestedrecently to polycondense polyamide-forming substances in the presence ofa small amount of a phosphinic compound selected from the groupconsisting of monoand di-alkyl, monoand di-aryl, and monoalkyl monoarylphosphinic acids, and diamine salts of these phosphinic acids. Theresulting polymers prepared in the presence of these additives exhibitgreater dye receptivity. However, when the polymers containing theaforesaid phosphinic additives are melt spun, obnoxious fumes heretoforehave developed during melt spinning giving rise to a health hazard tooperators attending the melt spinning operation.

It is an object of the present invention to provide a method of treatingnylon chips containing an organic derivative of hypophosphorous acid ordiamine salt thereof to minimize the formation of obnoxious fumesnormally occurring during melt extrusion of the chips into filaments orthe like.

It is a further object of the present invention to provide a method oftreating nylon-66 chips containing a phenylphosphinic compound tominimize the formation of obnoxious fumes normally occurring during meltspinning of the chips into filaments or the like.

Other objects may become apparent from the follow ing detaileddescription.

In general, the objects are accomplished by polycondensing anylon-forming substance in the presence of a small amount of aphosphinic additive. The phosphinic additive can be a compound selectedfrom the group consisting of monoand di-alkyl, monoand di-aryl, andmonoalkyl monoaryl phosphinic acids, and the diamine salts of thesephosphinic acids. Preferably, the additive Patented May 31, 1966 isbenzenephosphinic acid or hexamethylene diammoniumphenylphosphinate andthe nylon-forming substance is hexarnethylene diammoniumadipate. Theresulting nylon polymer is extruded and quenched in the form of a ribbonwhich is thereafter cut into flakes, chips, granules, or likeparticulate form. The chips are scoured to reduce the water solublecontent of the phosphinate additive. The scoured chips are dried andthen melted. The resulting polymer melt is extruded into filaments byconventional melt spinning. The thus-produced filaments exhibit anenhanced dye receptivity. Obnoxious phosphorous-containing fumesnormally attendant with melt spinning of chips which have not beenscoured is minimized. Surprising is the fact that the dye receptivity ofthe filaments is not reduced significantly by the scouring.

At least one of the above-defined phosphinic additives is introducedinto the polymerization vessel with the nylon-forming substance for thepurpose of enhancing the dye receptivity of filaments made from theultimate polymer. The phosphinic additives generally are used in anamount of about 0.7 to 14.0 mol percent based on the weight of thenylon-forming substance With about 0.7 to 2.0 mol percent beingpreferred. The additive should be a member of the class of phosphiniccompounds as above defined. For example, metal phosphinates, such assodium phenylphosphinate, to a substantial extent do not improve the dyesaturation level of nylon prepared in the presence thereof. Commerciallyimportant of the dye enhancing phosphinic additives arebenzenephosphinic acid or such acid which has been reacted with asuitable diamine such as hexarnethylene diamine to form hexamethylenediammoniumphenylphosphinate. In a preferred embodiment hexamethylenediammoniumadipate and benzenephosphinic acid are charged to apolymerization vessel conventionally used in preparing nylon polymer.Nylon-forming reaction conditions are employed. That is, the reactantsare heated at a temperature from about 180 C. to 300 C., and preferablyfrom 200 C. to 295 C. until the product has a sufficiently highmolecular weight to exhibit fiber-forming properties. This condition isreached when the nylon polymer possesses an intrinsic viscosity of atleast 0.3.

In a conventional manner the resulting nylon polymer is castinto aribbon which is quenched. As is normally the case where filaments arespun in accordance with the heated grid spinning procedure, the ribbonis diced into chips or flakes of the usual size. ent invention the chipsare scoured. That is, they are contacted with a solvent so that solublephosphinic compound is partly or totally removed from the chips. It hasbeen found that Water or water containing a small amount of an alkalinesubstance gives excellent results as a material with which the chips canbe scoured. The scouring can be accomplished in a variety of ways. Inone procedure the chips can be soaked in or drenched with water. Forbest results the scouring water has a pH of about 6 to 12.5, preferably6 to 8, and a temperature of about 20 C. to 100 C. and higher.Preferably the scouring is carried out at or near the boiling point ofwater. The-scouring time normally will be between about 5 and minutes toreduce the soluble phosphinic compound to a minimum practical value.

An alkaline substance which has been found to give good results istrisodium phosphate. It is believed that the scouring operation removesthe part of the phosphinic additive which has not become an integralpart of the nylon polymer. However, the presence of the part of thesoluble phosphinic additive is not really needed in the deeper dyeingfilaments, since filaments prepared with and without the scouring of thechips exhibit comparable dye receptivities.

However, in the pres- The scoured chips are dried in a suitable mannerwithout degrading the polymer to a substantial extent. For example, thechips can be dried in a vacuum oven at a temperature of 65 C. to 90 C.or centrifuged until .a moisture content of about two percent or loweris reached. The chips need not be dried completely, since the presenceof some water can be used to create a static pressure head of steamnormally maintained in melting Examples [-111 A stainless steelautoclave was charged with 406 parts of hexamethylene diammoniumadipatedissolved in an equal weight of water. A sufficient amount of aceticacid was added to stabilize the viscosity of the ultimate polymer at arelative viscosity of 34. The autoclave which-had been purged of air bysteam was pressurized and heated. When a temperature of 170 C. wasreached, 3.1 parts of benzenephosphin-ic acid was added. The heating ofthe ture to a temperature of 243 C. while the pressure was 1 heldconstant. At this point, the pressure reduction cycle was begun with thepressure being reduced to atmospheric pressure over a period of 105minutes. The polymerforming material was held at this temperature and atatmospheric pressure for an additional 30 minutes. The molten polymerthus obtained was then extruded in the form of a ribbon using aconventional casting wheel. After being cooled, the ribbon was cut intoflakes suitable for melting and spinning into filaments by means of amelt spinning assembly including a heated grid.

The polymer flakes were divided into three equal portions. One portionof the flakes was placed in an extraction tray wrapped with an aluminumscreen and suspended in a clean tank. The tank was rectangular with anopen top having a capacity of approximately 50 gallons. The bottom andsides of the tank were jacketed for reception of steam. The tank wasthen filled with deionized water having a pH of 6.7. The Water washeated to boiling and this condition was continued for a period of 30minutes. Thereafter, the steam was turned off and the water drained fromthe tank. This extraction procedure was then repeated twice after whichthe flakes were removed from the tank and transferred to a vacuum oven.The flakes were dried therein for a period'of 8 hours at 75 C; undervacuum.

The thus-prepared water-scoured flakes were then spun into textilefilaments using a conventional melt spinning apparatus. The air employedto solidify the filaments was analyzed for phosphorous content and wasfound to contain less than 0.05 ppm. phosphorous.

The second portion of the flakes was spun into textile filamentsby-passing the scouring and drying steps of the present invention. Theair employed to solidify the filaments had a pungent obnoxiousphosphorous-like odor.

The third portion of the flakes was placed in a bag constructed ofloosely woven nylon yarn. The bag was placed in boiling water containing2.5 gms./ liter trisodium phosphate for 30 minutes. The pH of the watercontaining the trisodium phosphate was 11.4. The flake was then dried ina vacuum oven for 8 hours at 75 C. The thus-scoured flakes were spuninto textile filaments using a conventional melt spinning apparatus. Theair employed to solidify the filaments was analyzed for phosphorouscontent and was found to contain less than 0.05 p.p.m. phosphorous.

There were no significant differences in the physical properties of thefilaments prepared from the scoured flakes and the unscoured flakes. Thefilaments obtained by spinning scoured flakes and unscoured flakes wereseparately fabricated into 4 inch length samples of knit tubing. Testswere .then run on each of the fabric samples to determine their relativedye saturation levels. In the procedure used, each of the samples wasdyed with equal concentrations of the commercial dyestutf Scarlet 4'RA(C.I. Acid Red 18). The dyeing was continued over a period of two hoursin a bath having a liquor to fiber ratio of 40:1. A temperature of C.was maintained in the bath. After completing the dyeing, the amount of.dye absorbed by each sample was determined by spectrophotometricallymeasuring the change in dye bath concentration, i.e., the differencebetween the original dye concentration in the bath and the exhausted dyeconcentration.- It was found that the amount of dye absorbed by thefilaments spun from scoured flakes was substantially the same as theamount absorbed by the filaments spun from unscoured flakes. Valuesobtained averaged 1.95 percent dye absorbed for scoured sample-s vs.2.08 percent for unscoured samples vs. 1.04 percent for samples notcontaining the phosphinic additive.

Example IV Another batch of polymer was prepared as described in ExampleI. The flakes were poured into a tray and immersed in boiling deionizedwater. After 30 minutes the tank was drained and refilled with freshdeionized water. The temperature of the water was raised to the boilingpoint and the extraction process was repeated. After repeating theextraction a third time, the chips were removed from the tray and dried.

- The washed and dried chips were placed in a conventional grid melterand the resulting melt extruded into filaments. The occurrence of theobnoxious fumes was reduced below the detectable level.

As can be seen from the above, the present invention affords severaladvantages. Nylon polymer to which a phosphinic compound has been addedduring the polycondensation thereof can be spun without the normalobnoxious phosphorous-containingfumes being formed during melt spinningof the polymer. The dye receptivity induced by the phosphinic compoundis not sacrificed by the scouring of the nylon flakes. The healthhazards of the fumes are obviated. Other advantages will be noted.

It is not intended that the invention be limited solely to the detailsof the embodiments set forth above. It will be recognized that numerousmodifications conforming to the spirit of the invention may be made.Therefore, it is intended that the invention be limited only by thescope of the following claims.

What is claimed is:

1. A process of treating chips of polyhexamethylene adipamidepolycondensed in the presence of about 0.7 to 14.0 mol percent based onthe weight of the polymer forming substance of a dye-enhancingbenzenephosphinic additive comprising the steps of:

(a) scouring said chips in water; and

(b) drying the scoured chips; whereby obnoxious phosphorous-containingfumes normally attendant with melt spinning of such polymer isminimized.

2. The process of claim 1 wherein the additive is ben-.

zenephosphinic acid.

3. The process of claim 2 wherein the pH of the scouring water is about6 to 12.5.

4. The process of claim 3 wherein the temperature of the scouring wateris about 20 C. to 100 C.

5' 6 5. The process of claim 2 wherein boiling Water of 21 2,927,8413/1960 Ben 26()-78 pH of about 6 to 8 is employed during the scouring.2,978,439 4/1961 Kersting 260--78 6. The process of claim 5 wherein asmall amount of 2,981,715 4/1961 Ben 26078 an alkaline substance ispresent in the scouring water. 3,078,248 2/ 1963 Ben 26,078

7. The process of claim 6 wherein boiling water con- 5 OTHER REFERENCEStaining a small amount of trisodium phosphate is employm during thescouring Beilstein: Organische Chemie, vol. 16, pp. 791 and 803 A Irelied on. References Cited by the Examiner WILLIAM H SHORT P E e UNITEDSTATES PATENTS 10 "7 2,510,777 6/1950 Gray 260-78 LOUISE QUAST Examme"2,739,959 3/ 19-56 ;Ney et al. 26078 H. D. ANDERSON, Assistant Examiner.2,891,038 6/1959 Barnes et al. 26078

1. A PROCESS OF TREATING CHIPS OF POLYHEXAMETHYLENE ADIPAMIDEPOLYCONDENSED IN THE PRESENCE OF ABOUT 0.7 TO 14.0 MOL PERCENT BASED ONTHE WEIGHT OF THE POLYMER FORMING SUBSTANCE OF A DYE-ENHANCINGBENZENEPHOSPHINIC ADDITIVE COMPRISING THE STEPS OF: (A) SCOURING SAIDCHIPS IN WATER; AND (B) DRYING THE SCOURED CHIPS; WHEREBY OBNOXIOUSPHOSPHOROUS-CONTAINING FUMES NORMALLY ATTENDANT WITH MELT SPINNING OFSUCH POLYMER IS MINIMIZED.